Although motor fuel revenues skyrocketed due to higher pump prices, fuel gallons sold last year declined 0.4 percent from 2010. Motor fuel gross margins increased from 15.8 cents to 18.4 cents per gallon before expenses, but dipped on a percentage basis from 5.64 percent to 5.23 percent.

A smaller part of the industry's 2011 sales growth can be attributed to an increase in store count, according to NACS. The number of U.S. convenience stores grew 1.2 percent over the past year to a record 148,341 locations, according to the NACS/Nielsen TDLinx Convenience Industry Store Count, released this January. Convenience stores now account for 34.6 percent of all retail outlets, according to Nielsen's figures.

NACS pointed out that convenience stores remain an important part of the economy, employing 1.88 million people and generating $162 billion in federal, state and local taxes last year. Between motor fuels and in-store operations, the average store had 1,130 transactions per day. Cumulatively, the industry conducted roughly 160 million transactions per day in 2011.

As in past years, while motor fuels drove sales dollars, in-store sales drove profit dollars. Overall, 71.4 percent of total sales were motor fuels, but motor fuels only accounted for 35.9 percent of profit dollars. Convenience store pretax profits reached a record $7 billion in 2011, but taken as a percent of total sales, profits fell from 1.146 percent to 1.027 percent of total sales, largely because of a 23-percent increase in debit and credit card fees, which hit a record $11.1 billion.

Total credit and debit card fees surpassed overall convenience store industry profits for the sixth straight year, and are now 87 percent higher than overall industry profits. As a percentage of overall sales, credit and debit card fees equaled 1.63 percent of total industry sales dollars, factoring in all forms of payment, including cash and check. Just looking at motor fuel sales, credit and debit card fees added 5.7 cents to every gallon of gasoline sold at c-stores in 2011.

"Our strong performance in 2011 shows that our industry's core convenience offer -- especially one-stop shopping and speed of service for refreshments, food and fuel -- continues to resonate with our customers and attract shoppers to our stores," NACS Chairman Tom Robinson, president of Santa Clara, Calif.-based Robinson Oil Corp., said at the State of the Industry Summit.

More than 80 percent of in-store sales last year came from the top five categories:

Cigarettes (38.1 percent of in-store sales)

Foodservice, including dispensed beverages (16.9 percent)

Packaged beverages (14.3 percent)

Beer (7.3 percent)

Other tobacco products (4 percent)

While tobacco products (cigarettes and other tobacco products) constituted more than 42.1 percent of in-store revenue dollars, they accounted for only 22.2 percent of gross margin dollars. Meanwhile, packaged beverages and foodservice continued to gain share of gross profit dollars and accounted for nearly half (47.8 percent) of all gross profit dollars, for which the top five categories are:

Foodservice (29.4 percent of in-store gross margin dollars)

Packaged beverages (18.4 percent)

Cigarettes (18.1 percent)

Beer (4.5 percent)

Candy (4.4 percent)

Several other areas of the business showed strong profit growth: lottery commissions grew 14.3 percent, while car wash increased a strong 75.4 percent and other automotive services increased 36.1 percent, according to NACS.

The convenience retail industry continued to separate between the haves and have nots. Top-quartile performers had gross profit dollars that were at least double that of bottom-quartile performers across the board. Top performers also enjoyed hot dispensed (mostly coffee) profits that were seven times higher than bottom-quartile performers, cold dispensed profits four times higher, and salty snacks and prepared food profits that were each three times higher than the bottom-quartile performers.